The Wonder Book of Knowledge: The Marvels of Modern Industry and Invention, the Interesting Stories of Common Things, the Mysterious Processes of Nature Simply Explained
History
The Wonder Book of Knowledge: The Marvels of Modern Industry and Invention, the Interesting Stories of Common Things, the Mysterious Processes of Nature Simply Explained
Industrial arts -- History
To get our picture as it should be, we must place the negative in
contact with a sheet of paper coated with a gelatine containing silver.
This emulsion, as the coating is called, is, as we might readily infer
from the presence of the silver, sensitive to the action of light in
much the same manner as was the original film. We place the negative and
paper in contact, then, in what is called a printing frame, so that
light may shine through the negative and impress the image on the
sensitive paper. It is obvious that the light parts of the negative will
let through the most light, and that consequently the silver emulsion on
the paper underneath will be most blackened, while the dark parts will
hold back the light and the emulsion on the paper underneath will be
less affected. In other words, the very faults that we noted in the
negative, from a picture point of view, automatically right themselves.
Mother’s dress looks dark and baby’s dress white--just as the lens saw
it.
We then have the picture in its finished form.
The story of the making of the camera is as interesting as that of the
making of the pictures by the camera.
Back in 1732, J. H. Schulze discovered that chloride of silver was
darkened by light and all unwittingly became the father of photography.
In 1737, Hellot, of Paris, stumbled on the fact that characters written
with a pen dipped in a solution of silver nitrate would be invisible,
until exposure to light, when they would blacken and become perfectly
legible. However, it was not until early in the nineteenth century that
these two discoveries were put to any practical use, as far as
photography was concerned.
People of an artistic turn of mind had been in the habit of making what
were called “silhouettes.” The sitter was so posed that the light from a
lamp threw the profile of his face in sharp shadow against a white
screen. It was then easy enough to obtain a fairly accurate silhouette,
by either outlining the profile or cutting it out from the screen.
Public-domain text, read in full here on John Shaqi.
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